linux-kernel - Re: [uml-devel] fuzz tested 32 bit user mode linux image hangs in radix_tree_next

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Message-ID: <527E8E19.9030802@nod.at>
Date:	Sat, 09 Nov 2013 20:33:45 +0100
From:	Richard Weinberger <richard@....at>
To:	Toralf Förster <toralf.foerster@....de>
CC:	Konstantin Khlebnikov <koct9i@...il.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	UML devel <user-mode-linux-devel@...ts.sourceforge.net>
Subject: Re: [uml-devel] fuzz tested 32 bit user mode linux image hangs in
 radix_tree_next_chunk()

Am 09.11.2013 20:07, schrieb Toralf Förster:
> On 11/06/2013 10:31 PM, Richard Weinberger wrote:
>> Am 06.11.2013 22:18, schrieb Toralf Förster:
>>> On 11/06/2013 05:06 PM, Konstantin Khlebnikov wrote:
>>>> In this case it must stop after scanning whole tree in line:
>>>> /* Overflow after ~0UL */
>>>> if (!index)
>>>>   return NULL;
>>>>
>>>
>>> A fresh current example with latest git tree shows that lines 769 and 770 do alternate :
>>
>> Can you please ask gdb for the value of offset?
>>
>> Thanks,
>> //richard
>>
> 
> Still trying to get those values. One attempt to do that was to replace -O2 with -O0 in the Makefile,
> but that resulted into this error :
> 
>   LD      kernel/built-in.o
>   CC      mm/memory.o
> In function ‘zap_pmd_range’,
>     inlined from ‘zap_pud_range’ at mm/memory.c:1265:8,
>     inlined from ‘unmap_page_range’ at mm/memory.c:1290:8:
> mm/memory.c:1220:23: error: call to ‘__compiletime_assert_1220’ declared with attribute error: BUILD_BUG failed
> mm/memory.c: In function ‘follow_page_mask’:
> mm/memory.c:1530:18: error: call to ‘__compiletime_assert_1530’ declared with attribute error: BUILD_BUG failed
> make[1]: *** [mm/memory.o] Error 1
> make: *** [mm] Error 2
> 
> 
> With -O1 it compiled at least.

You cannot build Linux with -O1/O0.
Try printing the value using printk...

Thanks,
//richard
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